What Is a Contrast Checker?
A contrast checker measures the luminance difference between a foreground color (typically text) and a background color, then expresses it as a ratio. That ratio tells you whether the pairing is readable for people with low vision or color deficiencies. The WCAG 2.2 specification sets the thresholds: normal text needs at least 4.5:1 for Level AA and 7:1 for AAA, while large text (18 pt or 14 pt bold) requires 3:1 for AA and 4.5:1 for AAA. This tool calculates those ratios in real time so you can verify compliance before shipping any design.
How to Use This WCAG Contrast Checker
- Enter two colors — paste HEX codes or use the color pickers for foreground and background. Hit Swap Colors to reverse the pair instantly.
- Read the ratio — the contrast ratio updates live, with clear AA and AAA pass/fail badges for normal text, large text, and non-text UI elements.
- Preview on real components — scroll to the live preview to see your colors applied to paragraphs, headings, buttons, tags, and links so nothing looks off in context.
- Simulate color blindness — toggle protanopia, deuteranopia, tritanopia, or achromatopsia to confirm the pairing holds up across different vision conditions.
- Export or share — copy results, download a summary, or generate a shareable link for team review.
Why Use an Online Color Contrast Checker?
Eyeballing color pairings is unreliable — subtle differences in luminance that look fine on one display can fail on another. An online color contrast checker removes that uncertainty by applying the WCAG relative-luminance formula to every pair you test. This is especially important for UI designers balancing brand aesthetics with accessibility contrast ratio requirements, and for developers who need to document compliance before code review.
This tool goes further than a basic ratio calculator. The built-in component preview shows how your colors behave on buttons, form elements, and inline links — exactly the contexts where WCAG 1.4.11 non-text contrast applies. And the color blindness simulation means you can catch issues that a contrast ratio alone won't reveal, without installing a separate browser extension.
WCAG Contrast Thresholds at a Glance
Normal text (below 18 pt or below 14 pt bold) must hit 4.5:1 for AA and 7:1 for AAA. Large text (18 pt and above, or 14 pt bold and above) lowers the bar to 3:1 for AA and 4.5:1 for AAA. Non-text elements — icons, input borders, focus rings — require at least 3:1 under AA. Logos and decorative content are exempt. When a pair falls short, try adjusting lightness in the color converter or generating a compliant alternative with the color harmony generator.
Tips for Fixing Failing Pairs
- If a color combination misses AA, small lightness shifts often solve the problem without changing brand hue. Darken the foreground or lighten the background until the ratio crosses 4.5:1. For full-palette auditing — especially design systems with dozens of token pairings — run every combination through the palette accessibility matrix to catch failures at scale. And when you need to see how the adjusted colors look under different vision conditions, the color blindness simulator lets you verify the fix visually before committing.